Add Support for Service Principal and Managed Identities

[Pratted]

Microsoft recently added support for Service Principal and Managed Identity authentication to Azure DevOps.

https://devblogs.microsoft.com/devops/introducing-service-principal-and-managed-identity-support-on-azure-devops/

It would be useful if these additional authentication methods could be added so we can run go programs in an automated fashion on behalf of a service account instead of relying on a user's PAT.

[XtratusCloud]

Adding this functionality would also unlock the possibility to include it in the azuredevops provider for terraform.

Please include in your roadmap

[hacker1db]

@Pratted I made a #141 This should address this issue.